According to known manual pumps of this type, the passage of hydraulic fluid through the second channel is automatically controlled by means of a control valve in this second channel. The valve in the second channel opens at the beginning of each power stroke when the predetermined level of pressure in the piston chamber is exceeded, so that pressure compensation occurs continuously between the piston chamber and the rod chamber. The effective pump surface is thereby reduced to the size of the rod surface. The force being exerted on the piston with the power stroke is then automatically reduced as soon as the aforementioned limit value is exceeded. Because of this, the use of a two-stage pump has been recently discussed, which can be used in lift trucks, whereby the loads are to be lifted with as few as possible pump cycles.